1. Field of the Invention
The present invention relates to a method for producing a formed wooden article, in particular, to a method for producing a structure with high strength, which is comparatively thin, and has substantially constant thickness, for example, a structure such as a box, a casing, a container, a cover, or a shell-shaped member, which has an opening at one side, by compressing and forming a wooden material.
2. Description of Related Art
Conventionally, it has been proposed that, through press-forming a plate-shaped wooden material in an atmosphere of water vapor at high temperature by using molding dies, a three-dimensionally shaped formed wooden article be produced.
Generally, since a wooden material is aggregate of wooden fibers in which cell walls extend in the growing direction of the wood, the strength in the fibrous direction remarkably differs from the strength in the direction orthogonal to the fibrous direction. For example, if a wooden material is bent around an axis orthogonal to the fibrous direction, mainly a tensile force acts on the wooden fibers, and the wooden material presents a comparatively high strength. However, if the wooden material is bent around an axis parallel to the fibrous direction, the wooden fibers are easily torn apart, the strength is low and cracks are easily brought about.
It is known that a blank plate should be obtained by primarily compressing a wooden material which is an aggregate of wooden fibers, and the blank plate should be further formed by secondarily compressing in order that the wooden fibers may not be torn apart by a tensile force acting among the wooden fibers while being formed.
For example, Japanese Unexamined Patent Application, First Publication No. H08-25301 describes a method for processing a wooden material, in which a plate-shaped primarily fixed article is formed by compressing a square lumber in the direction orthogonal to its fibrous direction and slicing the same, the primarily fixed article is mounted in forming dies with the periphery thereof restricted, and a secondarily fixed article having a three-dimensional shape is obtained by heating the primarily fixed article, causing the same to absorb water, and forming the same.
Also, Japanese Unexamined Patent Application, First Publication No. H11-77619 describes a method for processing a wooden material three dimensionally, in which a wooden material is compressed in a direction orthogonal to the fibrous direction and is sliced to get a wooden plate, which is bent around an axis parallel to the fibrous direction and is temporarily fixed as it is, and three-dimensional forming is carried out with the convex of the bent wooden plate matched to the convex of a press mold.